Multichannel Systems MC_Rack Manual - Manual (Page 140)

MC_Rack Manual
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4.12 Filtering Data
4.12.1 Filtering Data
The Digital Filter tool can be used online or offline. Displays in dependence of filters can show
the unfiltered and filtered data stream at the same time, so it is possible to directly monitor
the effect of the filtering on the data. This is especially important because all filters are known
to distort signals. Keep in mind that you may need a higher sampling rate to avoid aliasing.
Please see also chapter "Filtering and Sampling Rate" for more information about aliasing.
The filter tool creates a separate data stream that will show up in dependent displays and
instruments, as well as in the recorder. More than one filter can be used in combination on
the same data stream (one filter type after the other). However, this option consumes a lot
of system resources and can in some cases lead to performance problems. A range of filter
types are available, please see chapter “Filter Characteristics” below for a short description.
Click Edit drop down menu “Add Filter”. Select “Filter” tab.
Filter types: Bessel 2nd order
Bessel 4th order
Butterworth 2nd order
Chebyshev 2nd order, 0.5, 1.0, 2.0 and 3.0 dB
Bandstop Resonator
Savitzky Golay
Filters can be used to remove background noise from signals or to separate signal components
with different frequencies. The filter creates a separate data stream that can be recorded or
further processed. For example, you can use a high pass filter to separate spikes from slow field
potentials, and afterwards detect and analyze spikes on the filtered data.
The low pass filter preserves frequencies below passband; frequencies above stop band are
removed, with a smooth transition in-between. The high pass filter preserves high frequencies.
Note: All filters distort signals, so use the filter carefully!